The present invention relates to a direct radiography system in which subjective sharpness of an image can be improved by using silver halide photosensitive materials for one-sided direct radiography use and film charging mistakes can be avoided.
Two sided films in which silver halide emulsion layers are coated on both sides of a support, have been conventionally used for direct radiography.
In using two-sided films, high sensitivity and high image density can be obtained. On the other hand, two sided-films are theoretically and actually inferior to one-sided films in terms of image sharpness obtained after development because sharpness of a two-sided film deteriorates when the angle of incidence is not right-angled and because of the cross over effect.
Recently, one-sided films have been used for direct radiography of breasts and ear bones and for tomography in order to obtain images of better image sharpness.
One-sided film consists of a layer of photosensitive silver halide emulsion coated only on one side of a support. Accordingly, an intensifying screen for X-ray use is used only on one side.
For that reason, when film is put into a cassette in a dark room, the photosensitive material surface of the film must properly come into contact with the intensifying screen surface. Each manufacturer of film provides a notch in a specific position of the film in order to determine easily whether the photosensitive material surface is the front side or the rear side of the film.
However, the shapes and positions of film notchs are not standard and are different depending on the kind of film and the manufacturer. Consequently, when the film is charged into a cassette in a dark room, film charging mistake tends to occur.
The object of the present invention, therefore is to provide a one-sided direct radiography system which is characterized in that film can be charged easily into a cassette in a dark room and film charging mistakes caused by the misjudgment of the film side, can be avoided.
Other objects will become apparent from the following description of the invention.